Final answer:
To estimate the after-tax cost of debt, calculate the yield to maturity (YTM) of the existing bonds and adjust it for the after-tax cost by multiplying it by (1 - tax rate). The reasonable estimate for AL's after-tax cost of debt is 4.87% (option B).
Step-by-step explanation:
To estimate the after-tax cost of debt, we need to calculate the yield to maturity (YTM) of the existing bonds. The YTM is the rate of return that equates the bond's present value with the market price. Given that the bonds have a face value of $1,000, a coupon rate of 12%, and a market price of $1,329.55, we can use these values to calculate the YTM. After calculating the YTM, we adjust it for the after-tax cost of debt by multiplying it by (1 - tax rate). Therefore, the reasonable estimate for AL's after-tax cost of debt is 4.87% (option B).